Weak Antifungal Activity Research Articles

Synthesis and antimicrobial activity of functionally substituted 1,3-dioxacycloalkanes

One of the directions in the development of organic chemistry is the synthesis of biologically active compounds, including those with bactericidal activity, based on available petrochemical raw materials. In order to expand the library of bioactive compounds containing a 1,3-dioxacyclane fragment, the synthesis of derivatives of 5-acyl-5-isopropyl-1,3-dioxane – 1-(5-isopropyl-1,3-dioxane-5-yl)ethanol and (5-isopropyl-1,3-dioxane-5-yl)ethyl phenyl carbamate was carried out. The effect of synthesized compounds containing a 1,3-dioxacyclane fragment on the growth of strains of gram-negative and gram-positive bacteria, lower fungi Candida albicans was studied. It was found that 2-methyl-2-ethyl-4-chloromethyl-1,3-dioxolane, containing a chloromethyl group, has an antimicrobial effect against gram-positive and gram-negative test cultures and weak antifungal activity (minimum inhibitory concentration is 100 μg/mL) against lower fungi Candida albicans. 1-(5-Isopropyl-1,3-dioxan-5-yl)ethanol exhibits antifungal activity (minimum inhibitory concentration is 2 μg/mL) and sharply reduces antimicrobial activity against Klebsiella pneumonia, Staphylococcus aureus, Enterobacter aerogenes (minimum inhibitory concentration is 100 μg/mL), in contrast to the structurally similar 2-methyl-2-ethyl-4-hydroxymethyl-1,3-dioxolane, which did not show similar properties. 5-Acyl-5-isopropyl-1,3-dioxane, containing a carbonyl group in its structure, showed antimicrobial activity (minimum inhibitory concentration is 25 μg/mL) against gram-negative test cultures, with the exception of Pseudomonas aeruginosa. Heterocycles (2-methyl-2-ethyl-4-chloromethyl-, 2-isobutyl-2,4-dimethyl-, 2-methyl-2-isobutyl-4-chloromethyl- and 2-methyl-2-isobutyl-4-hydroxymethyl-1,3-dioxolane) at concentrations up to 100 μg/mL did not inhibit the vital activity of the studied bacteria and lower fungi. The results obtained show the prospect of continuing the search for new antimicrobial and antifungal drugs of the series of 1,3-dioxacycloalkanes, the structure of which is fundamentally different from the known antibacterial drugs.

Antifungal Activity of Butterfly Pea Flower (Clitoria Ternatea L.) against Candida Albicans Causes of Dandruff

Dandruff is a common scalp problem characterized by flaking, itching, and redness. One of the causes of dandruff is the fungus Candida albicans. Under certain conditions, such as excessive oil production, this fungus can grow and become pathogenic. Butterfly pea flower is a plant known to contain antifungal compounds, including tannins, flavonoids, saponins, and alkaloids. This study aims to determine the antifungal activity of ethanol extract from butterfly pea flower against Candida albicans using SDA (Sabouraud Dextrose Agar) medium with the disk diffusion method. The concentrations of butterfly pea extract used were 5%, 15%, 30%, 60%, and 90%. The positive control used was ketoconazole, while the negative control was 1% CMC-Na. The results of the study indicate that the butterfly pea extract exhibits antifungal activity, as evidenced by the formation of an inhibition zone at a concentration of 90%, with an average inhibition zone of 3.7 mm. The positive control showed an inhibition zone of 14.38 mm, categorized as strong. In contrast, the negative control did not show any inhibition zone due to the lack of antifungal activity. Based on these results, it can be concluded that butterfly pea (Clitoria ternatea L.) has the potential for weak antifungal activity against Candida albicans.

Reaping the Chemical Diversity of Morinagamyces vermicularis Using Feature-Based Molecular Networking.

Moringadepsin (6) and chaetone B (7) were isolated by us in the course of a conventional chemical screening of Morinagamyces vermicularis CBS 303.81, a fungus belonging to the relatively underexplored family Schizotheciaceae of the phylum Ascomycota. Since these metabolites did not account for the antifungal activity observed in a crude extract of this fungus, we utilized an MS/MS-based molecular networking approach to get a thorough insight into the secondary metabolites produced by this strain. Manual annotation of high-resolution fragmentation mass spectra by CANOPUS classified a major molecular family as putatively new thiodiketopiperazines. However, these results were opposite to the results of ChemWalker analysis based solely on MS/MS data, assigning these metabolites as various polyketides. Thus, targeted preparative HPLC isolation focusing on the most abundant features within this major molecular family resulted in the isolation of five secondary metabolites. Their structures were elucidated based on HRMS and NMR data as four new thiodiketopiperazine derivatives, botryosulfuranols D-G (1-4), alongside the known botryosulfuranol A (5). Compounds 1-3 and 5 exhibited moderate to weak antifungal activity against different test strains, accounting for the initial antifungal activity observed for its crude extract. Our study stressed the importance of full NMR-based structure elucidation for metabolomics research.

The Antiphytopathogenic Metabolites and the Synergy of Endophytes Paraphaeosphaeria sp., Nigrospora oryzae from the Same Ginkgo biloba Host.

Two endophytes from the same Ginkgo biloba host were isolated and cultured separately. Three new eremophilane sesquiterpenoids (1-3), three new furan derivates (6, 8-9), one new polyketide (10), and four known compounds (4, 5, 7, 11) from Paraphaeosphaeria sp. and two new 10-membered macrolides (12-13), a new liner polyketide (14), a new benzofuran (15), and six known compounds (16-21) from Nigrospora oryzae were isolated. The structures of the isolated compounds were determined by spectroscopic methods, NMR calculations, and ECD calculations. The compounds 3-7, 9-10, 12, and 14-17 showed significant antiphytopathogenic effects against mycotoxigenic Alternaria sp. comparable to the activity of nystatin (positive control). Compounds 2, 6, 8, 9, and 18 indicated inhibitions against phytopathogen Fusarium asiaticum with MICs < 10 μg/mL. In addition, the compounds with weak antifungal activities from two endophytes were mixed to test their antifungal activity. The results showed that the metabolites from two endophytes had synergistic antifungal effects, and the beneficial interactions between natural products can induce more antifungal effects against plant pathogens than that of single compounds.

ANTI-MICROBIAL ACTIVITY OF SOME Pt(II) COMPLEXES BEARING 8-OXYQUINOLINE (8-OQ) AND EUGENOL DERIVATIVE AND 3D-STRUCTURE OF COMPLEX [PtCl(8-OQ)(EUGENOL)

Four complexes including [PtCl(8-OQ)](arylolefin)] (arylolefin: Eug, M1; Aceug, M2, Eteug, M3, Preug, M4) were obtained by the reaction between 8-hydroxyquinoline and K[PtCl3(arylolefin)] in high yields. The 3D structure of M1 has been determined for the first time by DFT calculation combined with the experimental NOESY spectrum. The result showed that M1 exists as distorted square-planar coordination with angles of O-Pt-Cl and N-Pt-O of 176.4o and 81.0o respectively. In which 8-OQ coordinates with Pt(II) through both the N and O atoms, Eug bonds with Pt(II) via the C=Cally and in trans position to the N atom of 8-OQ. The investigation of the biological activities of the synthesized complexes showed that they display weak anti-bacterial and antifungal activities.

A new polyene macrolide antibiotic, machidamycin, produced by Streptomyces sp. K22-0017.

A new polyene macrolide, machidamycin (1), and a known compound YS-822A (2), were obtained by physicochemical screening from a culture broth of Streptomyces sp. K22-0017. The structures were elucidated using MS and 1D/2D NMR analyses. Compound 1 exhibited weak antifungal activity against Candida albicans and Mucor racemosus. Furthermore, 1 showed stronger antileishmanial activity than the existing drug paromomycin.

Endophytic Aspergillus hiratsukae mediated biosynthesis of silver nanoparticles and their antimicrobial and photocatalytic activities.

In the current study, endophytic Aspergillus hiratsukae was used for the biosynthesis of silver nanoparticles (Ag-NPs) for the first time. The characterizations were performed using X ray diffraction (XRD), Transmission electron microscopy (TEM), Scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM-EDX), Dynamic light scattering (DLS), Fourier transform infrared spectroscopy (FT-IR), and UV-Vis spectroscopy. The obtained results demonstrated the successful formation of crystalline, spherical Ag-NPs with particle diameters ranging from 16 to 31 nm. The FT-IR studied and displayed the various functional groups involved, which played a role in capping and reducing agents for Ag-NPs production. The SEM-EDX revealed that the main constituent of the AS-formed sample was primarily Ag, with a weight percentage of 64.2%. The mycosynthesized Ag-NPs were assessed for antimicrobial as well as photocatalytic activities. The antimicrobial results indicated that the synthesized Ag-NPs possess notable antibacterial efficacy against Staphylococcus aureus, Bacillus subtilis, and Escherichia coli, with minimum inhibitory concentrations (MICs) of Ag-NPs ranging from 62.5 to 250 μg/mL. Moreover, the biosynthesized Ag-NPs demonstrated weak antifungal activity against Aspergillus brasiliensis and Candida albicans, with MICs of 500 and 1,000 μg/mL, respectively. In addition, the mycosynthesized Ag-NPs exhibited photocatalytic activity toward acid black 2 (nigrosine) dye under both light and dark stimulation. Notably, After 300 min exposure to light, the nigrosine dye was degraded by 93%. In contrast, 51% degradation was observed after 300 min in darkness. In conclusion, Ag-NPs were successfully biosynthesized using endophytic A. hiratsukae and also exhibited antimicrobial and photocatalytic activities that can be used in environmental applications.

Four unreported aporphine alkaloids with antifungal activities from Artabotrys hexapetalus

In this study, the extract from Artabotrys hexapetalus showed strong antifungal activity against phytopathogenic fungi in vitro. Four unreported aporphine alkaloids, hexapetalusine A-D (1–4), were isolated from stems and roots of Artabotrys hexapetalus (L.f.) Bhandari, along with six known aporphine alkaloids (5–10). Their chemical structures were elucidated by extensive spectroscopic analysis. The absolute configurations of 1–3 were determined using single-crystal X-ray diffractions and ECD calculations. Hexapetalusine A-C (1–3) were special amidic isomers. Additionally, all isolated compounds were evaluated for their antifungal activity against four phytopathogenic fungi in vitro. Hexapetalusine D (4) exhibited weak antifungal activity against Curvularia lunata. Liriodenine (5) displayed significant antifungal activity against Fusarium proliferatum and Fusarium oxysporum f. sp. vasinfectum, which is obviously better than positive control nystatin, suggesting that it had great potential to be developed into an effective and eco-friendly fungicide.

Antimicrobial Activity and Molecular Docking of Benzoyl-N,N’-dialkylurea against Target Proteins in Microbial Cells

This research aims to evaluate the antimicrobial activity of benzoyl dialkylurea derivatives to meet the global need for new antibiotic lead compounds. Four compounds were tested in vitro against Staphylococcus aureus, Bacillus subtilis, Escherichia coli, Pseudomonas aeruginosa, and Candida albicans by broth dilution method using ciprofloxacin and nystatin as standards. Docking simulations were performed to target essential proteins including DNA gyrase, FabH, RNA polymerase in bacterial cells and DHFR in C. albicans. BDMU, BEU1, BEU2, BEU3 exhibited antibacterial activity while BEU1 and BEU2 showed weak antifungal activity against C. albicans. The BDMU, BEU2, BEU3 considered promising growth inhibition against P. aeruginosa. In silico molecular docking on DNA gyrase from P. aeruginosa (PDB. 6M1S) was proposed as a model for mechanism of action in bacterial cells. The monobenzoyl of dialkylurea containing urea functionality with chloro-substituent at position-2 and 4 on aromatic rings were potential as lead compound to generate new antibacterial agent.

A Highly Efficient, Catalyst-Free Synthesis of S-Alkyl/aryl Dithiocarbamate Derivatives under Green Conditions and Evaluation of their Biological Activity

An efficient, feasible, transition metal catalyst-free and environmental friendly approach for the synthesis of dithiocarbamate in an ethanol-water solvent combination at room temperature has been established. Alkyl/aryl halide, carbon disulfide and secondary amine were condensed in one pot to produce a range of dithiocarbamate derivatives. Based on the results, the yields were higher when aliphatic amine reacted with benzyl halides as compared to alkyl halides. This method has the advantage of using no hazardous solvents. Other benefits of this method include producing compounds with a good yield by a catalyst-free reaction employing a simple, affordable and useful method. When tested against specific pathogens, selected dithiocarbamate derivatives showed strong antibacterial activity but weak antifungal activity.

Antifungal Activity of Red Ginger (Zingiber officinale var. Rubrum) and Garlic (Allium sativum) against HIV Patients-Isolated Candida albicans

The most of Candida strain in oral candidiasis is nystatin resistance strain. Hence, it become important to investigate the natural products like red ginger (Zingiber officinale var. Rubrum) and garlic (Allium sativum) as antifungal against HIV patient-isolated Candida albicans. This experimental study used two antifungal assays (Disc diffusion and antibiofilm assay). Both red ginger and garlic extract were extracted by maceration method. Candida albicans isolate was isolated from a volunteer HIV Patient with oral candidiasis. The outcomes included the diameter of the inhibition zone and optical density (OD) that were expressed as mean and standard deviation and analysed by Kruskal-Walis. This study showed that the highest concentration of both red ginger (0.67 ± 0.55 mm) and garlic extract (0.67 ± 0.46 mm) had the widest diameter of inhibition zone. Meanwhile, the highest inhibition of biofilm formation was found in the lowest concentrations (25%) of red ginger (2.22 ± 1.24) and garlic extract (3.65 ± 0.24). Any concentration of red ginger or garlic extract did not significantly affect the antifungal activity (P-Value: 0.392). Overall, it can be concluded that both red ginger and garlic extract at any concentration showed a weak antifungal activity against HIV patient-isolated Candida albicans strain.

Thymus Vulgaris Oil Nanoemulsion: Synthesis, Characterization, Antimicrobial and Anticancer Activities.

Essential oil nanoemulsions have received much attention due to their biological activities. Thus, a thyme essential oil nanoemulsion (Th-nanoemulsion) was prepared using a safe and eco-friendly method. DLS and TEM were used to characterize the prepared Th-nanoemulsion. Our findings showed that the nanoemulsion was spherical and ranged in size from 20 to 55.2 nm. The micro-broth dilution experiment was used to evaluate the in vitro antibacterial activity of a Th-emulsion and the Th-nanoemulsion. The MIC50 values of the thymol nanoemulsion were 62.5 mg/mL against Escherichia coli and Klebsiella oxytoca, 250 mg/mL against Bacillus cereus, and 125 mg/mL against Staphylococcus aureus. Meanwhile, it emerged that the MIC50 values of thymol against four strains were not detected. Moreover, the Th-nanoemulsion exhibited promising antifungal activity toward A. brasiliensis and A. fumigatus, where inhibition zones and MIC50 were 20.5 ± 1.32 and 26.4 ± 1.34 mm, and 12.5 and 6.25 mg/mL, respectively. On the other hand, the Th-nanoemulsion displayed weak antifungal activity toward C. albicans where the inhibition zone was 12.0 ± 0.90 and MIC was 50 mg/mL. Also, the Th-emulsion exhibited antifungal activity, but lower than that of the Th-nanoemulsion, toward all the tested fungal strains, where MIC was in the range of 12.5-50 mg/mL. The in vitro anticancer effects of Taxol, Th-emulsion, and Th-nanoemulsion were evaluated using the standard MTT method against breast cancer (MCF-7) and hepatocellular carcinoma (HepG2). Additionally, the concentration of VEGFR-2 was measured, and the activities of caspase-8 (casp-8) and caspase-9 (casp-9) were evaluated. The cytotoxic effect was the most potent against the MCF-7 breast cancer cell line after the Th-nanoemulsion treatment (20.1 ± 0.85 µg/mL), and was 125.1 ± 5.29 µg/mL after the Th-emulsion treatment. The lowest half-maximal inhibitory concentration (IC50) value, 20.1 ± 0.85 µg/mL, was achieved when the MCF-7 cell line was treated with the Th-nanoemulsion. In addition, Th-nanoemulsion treatments on MCF-7 cells led to the highest elevations in casp-8 and casp-9 activities (0.66 ± 0.042 ng/mL and 17.8 ± 0.39 pg/mL, respectively) compared to those with Th-emulsion treatments. In comparison to that with the Th-emulsion (0.982 0.017 ng/mL), the VEGFR-2 concentration was lower with the Th-nanoemulsion treatment (0.672 ± 0.019ng/mL). In conclusion, the Th-nanoemulsion was successfully prepared and appeared in nanoform with a spherical shape according to DLS and TEM, and also exhibited antibacterial, antifungal, as well as anticancer activities.

Tandocyclinones A and B, Ether Bridged C-Glycosyl Benz[a]anthracenes from an Intertidal Zone Streptomyces sp.

Two new proton-deficient metabolites, tandocyclinones A and B (1 and 2), were discovered via the chemical profiling of the Streptomyces sp. strain TDH03, which was isolated from a marine sediment sample collected from the intertidal mudflat in Tando Port, the Republic of Korea. The structures of 1 and 2 were elucidated as new ether-bridged C-glycosyl benz[a]anthracenes by using a combination of spectroscopic analyses of ultraviolet (UV) and mass spectrometry (MS) data, along with nuclear magnetic resonance (NMR) spectra, which were acquired in tetrahydrofuran (THF)-d8 selected after an extensive search for a solvent, resulting in mostly observable exchangeable protons in the 1H NMR spectrum. Their configurations were successfully assigned by applying a J-based configuration analysis, rotating-frame Overhauser enhancement spectroscopy (ROESY) NMR correlations, chemical derivatization methods based on NMR (a modified version of Mosher's method) and circular dichroism (CD) (Snatzke's method using Mo2(OAc)4-induced CD), as well as quantum-mechanics-based computational methods, to calculate the electronic circular dichroism (ECD). Tandocyclinones A and B (1 and 2) were found to have weak antifungal activity against Trichophyton mentagrophytes IFM40996 with an MIC value of 128 μg/mL (244 and 265 μM for 1 and 2, respectively). A further biological evaluation revealed that tandocyclinone A (1) displayed inhibitory activity against Mycobacterium avium (MIC50 = 40.8 μM) and antiproliferative activity against SNU638 and HCT116 cancer cells, with IC50 values of 31.9 µM and 49.4 µM, respectively.

Trichoderols B-G, Six New Lipids from the Marine Algicolous Fungus Trichoderma sp. Z43.

Six new lipids, trichoderols B-G (1-6), along with a known one, triharzianin B (7), were isolated from the culture of Trichoderma sp. Z43 obtained from the surface of the marine brown alga Dictyopteris divaricata. Their structures and relative configurations were identified by interpretation of 1D/2D NMR and MS data. Compounds 1-7 were assayed for inhibiting the growth of three phytopathogenic fungi (Fusarium graminearum, Gaeumannomyces graminis, and Glomerella cingulata), four marine phytoplankton species (Amphidinium carterae, Heterocapsa circularisquama, Heterosigma akashiwo, and Prorocentrum donghaiense), and one marine zooplankton (Artemia salina). Compounds 1, 4, and 7 exhibited weak antifungal activities against three phytopathogenic fungi tested with MIC ≥ 64 μg/mL. All compounds displayed moderate antimicroalgal activity with IC50 ≥ 15 μg/mL and low toxicity to the brine shrimp Artemia salina.

Construction of lipopeptide mono-producing Bacillus strains and comparison of their antimicrobial activity

Bacillus amyloliquefaciens generally secretes a mixture of multiple cyclic lipopeptides, including iturin, surfactin, and plipastatin, and it is challenging to discriminate each cyclic lipopeptide's antimicrobial activity directly. In this study, a chassis strain Bacillus subtilis 1A751 WR without cyclic lipopeptides operons was constructed by CRISPR/Cas9. The iturin gene cluster of B. amyloliquefaciens HYM-12 was captured and assembled with sfp and degQ genes using transformation-associated recombination (TAR). It was then integrated into the chassis strain to obtain an iturin mono-producing strain that could synthesize six iturin isoforms. The frameshift sfp gene of strain 1A751 Δpps was repaired by a scarless gene knock-in method to generate a surfactin mono-producing strain. Antimicrobial activity experiments indicated that the extracts of iturin, surfactin, and our previously constructed plipastatin mono-producing strains exhibited powerful inhibitory effects toward pathogenic bacteria. Interestingly, iturin showed significant antifungal activity, but surfactin and plipastatin exhibited weak antifungal activity. Compared with amphotericin B, iturin has a solid and durable antifungal activity. This study demonstrates that TAR cloning is efficient for cloning large gene clusters, proves the differences in the antimicrobial activity of three cyclic lipopeptides, and lays a theoretical basis for further elucidating their antimicrobial mechanism.

Synthesis, structure and antibacterial, antifungal activities of some hydrazones synthesized from 4-hydroxy-3-nitrobenzaldehyde

Eight hydrazones 7a-h containing benzo[d]thiazole were synthesized in high yield by the condensation reaction of N-(5-(benzo[d]thiazol-2-yl)-2-(2-hydrazinyl-2-oxoethoxy)phenyl)acetamide (6) derived from 4-hydroxy-3-nitrobenzaldehyde with aromatic aldehydes under microwave irradiation. Structures of these derivatives 7a-h were elucidated by IR, NMR, and MS analysis. NMR spectra showed that in solution, hydrazones may exist in two conformations EN-C(O)ZN-C(O)EC=N and ZN-C(O)ZN-C(O)EC=N, the relative ratio of these two conformations is about 3:2. Four compounds 7a, 7c, 7e, 7g were screened for antimicrobial activities. Compounds 7c, 7e, and 7g exhibited weak antibacterial and antifungal activity against B. subtillis and S. cerevisiae, E. coli, or P. aeruginosa at 200 µg/L.

The antifungal metabolites from coculture of Aspergillus fumigatus and Alternaria alternata associated with Coffea arabica

One new cyclohexenone derivative, asperfumtone A (1) along with six known compounds were obtained from the coculture of Aspergillus fumigatus and Alternaria alternata associated with Coffea arabica. The configuration of 2 was first reported in the research. The structures were determined by extensive spectroscopic analyses, and ECD calculation. Compounds 3, 4 and 7 showed significant antifungal activities against coffee phytopathogens A. alternata and Fusarium incarnatum with MICs of 1 μg/mL. Compounds 1 and 2 showed weak antifungal activities against A. alternata and F. incarnatum with MICs of 32–64 μg/mL.

Aspergillus terreus-Mediated Selenium Nanoparticles and Their Antimicrobial and Photocatalytic Activities

Selenium (Se) is a nutritional component necessary for animal and plant development and reproduction. Selenium nanoparticles (SeNPs) have a high absorption rate during routine supplementation. In the current study, a cell-free extract of Aspergillus terreus was used as a reducing and stabilizing agent in the synthesis of SeNPs using a green and eco-friendly method. The mycosynthesized SeNPs were characterized by UV-visible spectrophotometry, Fourier transform infrared spectroscopy, X-ray diffraction spectroscopy, dynamic light scattering, transmission electron microscopy, and scanning electron microscopy. The results of the characterization process showed that the mycosynthesized SeNPs had spherical shapes and sizes less than 100 nm. Results showed that mycosynthesized SeNPs exhibited promising antibacterial activity against both Gram-positive and Gram-negative bacteria where inhibition zones were 14, 20, 16, and 13 mm toward S. haemolyticus, S. aureus, E. coli, and K. pneumoniae, respectively. However, it had weak antifungal activity against C. albicans, where the inhibition zone was 12 mm. The efficacy of mycosynthesized SeNPs for the decolorization of malachite green dye was investigated. Results illustrated that SeNPs exhibited rapid biodegradation of malachite green dye, reaching up to 89% after 240 min. In conclusion, SeNPs were successfully biosynthesized using A. terreus and demonstrated both antimicrobial and photocatalytic activities.

Assembly of an active microbial consortium by engineering compatible combinations containing foreign and native biocontrol bacteria of kiwifruit

Assembling functional bacterial biocontrol consortia is expected to expand the scope and efficiency of biocontrol agents. Generally, bacterial interspecies interactions lead to incompatibility events, as bacteria can produce antibacterial compounds and/or assemble contact-dependent killing (CDK) devices. Here, we aimed to assemble a bacterial consortium comprising Lysobacter enzymogenes OH11 and Bacillus safensis ZK-1 for the synergistic control of bacterial and fungal diseases of kiwifruit. ZK-1, a native kiwifruit biocontrol bacterium, is effective against Pseudomonas syringae pv. actinidiae (Psa) that causes bacterial kiwifruit canker, but has weak antifungal activity. OH11 is a foreign kiwifruit biocontrol agent with strong antifungal activity. While OH11 was unable to produce anti-Gram-negative metabolites, this strain could utilize type IV secretion system as an antibacterial CDK weapon. We first observed that OH11 could inhibit growth of ZK-1 by generating diffusible anti-Gram-positive antibiotic WAP-8294A2, whereas ZK-1 failed to generate diffusible antibacterial compound to inhibit growth of OH11. To disrupt this interspecies incompatibility, we generated a transgenic OH11-derived strain, OH11W, by deleting the WAP-8294A2 biosynthetic gene and found that OH11W did not kill ZK-1. We further observed that when OH11W and ZK-1 were co-inoculated on agar plates, no CDK effect was observed between them, whereas co-culture of OH11W or ZK-1 with Psa on agar plates resulted in Psa killing, suggesting L. enzymogenes and B. safensis assemble antibacterial CDK weapons against bacterial pathogens, and these CDK weapons did not affect the compatibility between OH11W and ZK-1. Based on these findings, we assembled an OH11W/ZK-1 dependent consortium that was shown to be functional in controlling bacterial canker and several representative fungal diseases of kiwifruit.

RELATIONSHIP BETWEEN PHYSICOCHEMICAL PARAMETERS AND ANTIMICROBIAL ACTIVITY OF MOLDAVIAN HONEY

Six samples of Moldavian honey from different regions were analyzed, physical and chemical parameters, the content of macro-, microelements, and aminoacids were determined, as well as antibacterial and antifungal activity. The antibacterial and antifungal properties were determined using the double serial dilution method. It was established that all of the samples of acacia, linden, and sunflower honey possess high antibacterial activity. The bioactivity of the samples of honey was proven to be dependent on the type and origin of honey. Sunflower honey has higher antibacterial potency than linden, but linden honey is more active than acacia. Both Gram-positive and Gram-negative bacterial species proved to be susceptible to Moldavian honey. Acacia, linden, and sunflower honey, possess high antibacterial potency against S. aureus and P. aeruginosa even at a dilution of 1:16 (2.5%). The studied samples showed weak antifungal activity against Candida albicans, with the MIC determined at 1:2 dilution (20%). For linden and sunflower honey, the antifungal activity was higher than for acacia honey. The samples with the best bioactivity (sunflower honey) contain a higher amount of free acids, had lower pH values of the honey solution, and these samples also have the highest content of OMF.